You are obviously grappling with your friend's death, and I appreciate the sophistication and sensitivity evident in your question.
I think it's crucial here to distinguish the meaning or "significance" of suicide from the meaning or significance of your friend's suicide. It's important that we resist what I think of as the easy mystification of suicide. There is an unfortunate tendency to infer from our inability to understand a particular suicide or to imagine ourselves engaging in the act ourselves that suicide is unfathomable, incomprehensible, or beyond reason. The truth is we understand a fair bit about the causes of suicide, have growing knowledge of how to prevent it, and so on. We should not let our emotional reaction to suicide -- whether it be shock, dismay, anger, whatever -- lead us to treat suicide as a "senseless" or trivial act.
That said, what we know about suicide in general can be difficult to extrapolate to particular people and cases. Individual people are in certain ways more...

Leaving aside the gargantuan question 'what constitutes a duty?', let's focus on the question of whether the elderly ever have a duty to die.
In a famous article http://web.utk.edu/~jhardwig/dutydie.htm, John Hardwig argues that some elderly or ill individuals have a duty to die. Very roughly, his thought is that one can have an obligation not to impose unfair burdens on others (financial, emotional, etc.). Since the ill or elderly often have medical conditions that are unduly burdensome to others, then if the only route to their avoiding imposing these burdens is for them to end their lives prematurely, then they have (according to Hardwig) a duty to die.
Hardwig's argument evoked a great deal of hostility when it was first published, and few philosophers have accepted it without controversy. Some of these criticisms are collected here http://www.amazon.com/There-Duty-Die-Bioethics-Reflective/dp/0415922429/ref=sr_1_1?s=books&ie=UTF8&qid=1453420574&sr=1-1&keywords=Hardwig+duty+to+die and http://www...

I'm not entirely sure I accept the assumption of your question: Is it really any more difficult to imagine life after death than life before death? Many philosophers have argued that it is difficult to imagine being dead because the act of imagination requires that one be alive. In other words, any attempt to imagine being dead is thereby a failure, some have argued. In imagining oneself dead, one must presuppose that there is a consciousness (a living one, presumably), so one cannot coherently imagine being dead — at least if that means imagining oneself being dead. Now if that's correct, then one similarly could not imagine the past before one existed. After all, in attempting to imagine the past, that would require you to be conscious and to be alive, etc. Of course, one might take this reasoning to show that it's not any harder to imagine life after death: Since we can imagine what existed before our birth, we can equally well imagine life after death.
So I'm not entirely convinced of the...

I gather that the worry behind your question is whether the dead really have "possessions" to be stolen: How can a dead person "possess" something? After all, they can't hold it, see it, use it, etc. But it's worth keeping in mind that stealing amounts to taking something that properly belongs to another — something in which that person has a property right . And having a property right and all that entails — having the right to preclude others from using an object, most importantly — does not seem to turn on our physical relation to an object. Whatever moral claim I have on my house, for example, doesn't turn on my actually being present in the house: My property right in the house is, as Kant put it, a matter of "intelligible possession". Others don't have the moral permission to occupy or use my property even when I am not using it or am not in physical possession of it. So I don't see that the fact that the dead are, well, dead and so can't possess their property in a literal sense is any...